1. Field of Invention
The present invention relates to the wet-processing systems used in microelectronic fabrication. More particularly, the present invention relates to the systems used for cleaning after microelectronic device manufacturing process steps such as the pre-diffusion cleaning, wet etch processes, photoresist removals and other cleaning operations.
2. Description of the Related Art
Particle contamination is an important source of semiconductor chip yield losses. As chip geometry becomes smaller, even very small particles, such as those less than 0.1 microns in diameter, can cause defects that decrease yield and product reliability. Despite the importance of this problem, major gaps exist in industry knowledge and technology. This problem is especially acute for the wet processes and rinse systems.
The microelectronic devices are typically processed using chemical solutions and rinses. For example, a semiconductor wafer is typically made from silicon with various materials implanted or diffused into or applied on the surface. During a wet etch step in the process, a group of wafers to be etched are placed in a container called a boat that is placed in a chemical solution. After this, the boat is removed from the chemical solution and rinsed with deionized (DI) water to stop the etch. The rinse can also help remove particles that happen to adhere to the wafer. Unfortunately, the water used in rinsing process can introduce particles that adhere to the wafer. Handbook of Quality Integrated Circuit Manufacturing by Robert Zorich, ISBN 012-781870-7 provides a description of circuit manufacturing techniques and concerns, and the entire disclosure is hereby incorporated by reference.
Some operations in semiconductor manufacture require that there be no oxide layer on the wafer. However, if any particles contact the bare wafer after bathing in hydrofluoric acid (HF) before a protective oxide layer is formed, the particles may strongly adhere to the wafer. Further, a thin protective oxide layer forming whenever bare silicon is exposed to oxygen may protect against further reactions and contaminants but will not always reduce particle contamination. For example, when the oxide layer is formed on the wafer from contact with air, water may not effectively rinse the particles from the surface.